• Modal Verbs

• 
• Use modal verbs to show ability/possibility, ask permission, make requests or offers, give suggestions, or give commands.  Always use modal verbs with a base verb.

  
  

  subject + modal verb + base verb

  
  

  Remember! You can also use modal verbs for negative statements and questions.
  
• Negative statements

  Add not after the modal verb.

  subject + modal + not + base verb
• Questions

  Start questions with a modal verb.

  modal + subject + base verb
•  Click on the play button to hear the audio

• You can do better in your senior year!	You have to submit your project on time!
  You should not* cheat on your final exam.	Professor, could you help me with this question?

• *Remember! You can combine modal verbs with not to form contractions. (should not >shouldn't)

 Source : Alison